JPH0418154B2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to multi-stage centrifugal compression for raw material air compressors used in oxygen production plants and various plants, compressors for factory air sources, gas compressors for chemical plants, etc. It concerns a method for controlling the capacity and pressure of a machine.

[Conventional technology]

Generally, centrifugal compressors in oxygen control plants and various plants are of multi-stage construction. In such a multistage centrifugal compressor,
As shown in FIG. 8, the centrifugal compressor 1 has a drive unit 2.
A first stage compressor 4, a second stage compressor 5, which are driven by a power transmission gear 3 that accelerates the rotation from
A third stage compressor 6 and a fourth stage compressor 7 are provided, and an intercooler 8 is provided between the compressors 4 and 5.
An intercooler 9 is provided between the compressors 5 and 6, and an intercooler 10 is provided between the compressors 6 and 7. In addition, compressors 4 and 5 and compressors 6 and 7
are overhanging the same axial end.

In such a centrifugal compressor 1, the air sucked into the first stage compressor 4 is transferred to each compressor 5 to
7 and intercoolers 8 to 10, and is sequentially compressed and cooled, and then sent to the process from the fourth stage compressor 7.

On the inlet side of each stage of compressors 4 to 7, angle-variable inlet guide vanes (GV) 11 to 14 are installed.
are provided, and these inlet guide vanes 11-1
By adjusting the angle of 4, each compressor 4-7
It is possible to adjust the amount of air flowing into the tank. In addition, differential user vanes (DV) 15 to 18 are provided on the outlet side of the compressors 4 to 7 in each stage, and these differential user vanes 15 to 18
By adjusting the angle of each compressor 4-7
It is possible to adjust the amount of air flowing out of the

The angles of these entrance guide vanes 11 to 14 and diffuser vanes 15 to 18 are each adjusted to arbitrary values by a drive device 19.

Further, the operating state of the entire centrifugal compressor 1 or the compressors 4 to 7 of each stage, for example, operating state quantities such as air flow rate, temperature, and pressure, are determined by a flow rate sensor 20, a temperature sensor 21, a pressure sensor 22, etc. is detected by the detection means. A control device 23 is provided between each of the sensors 20 to 22 and the drive device 19.

Conventionally, a control means as shown in FIG. 9 has been disclosed in order to control the multi-stage centrifugal compressor as described above so that a predetermined air capacity (flow rate) can always be obtained with optimum operating efficiency according to various operating conditions. (Tokkai Sho)
55-60692). In this control means, the operation amount is controlled to achieve the optimum operating state for various operating states expressed by air flow rate, temperature, pressure, etc. in the entire centrifugal compressor 1 or the compressors 4 to 7 in each stage. As, each stage inlet guide vane 11~
14 and the angles of the diffuser vanes 15 to 18 are programmed and stored in advance in the storage section of the control device 23 (step
SO).

Then, as shown in FIG. 9, the control device 23
When the system receives the state detection values from the sensors 20 to 22, it calculates and monitors the current operating state of the multistage centrifugal compressor from the detected values (step S1), and also performs predetermined operations corresponding to the operating state. The set operating program (combined values of vane angles) is compared to find the operating amount that can realize the optimum operating efficiency, and this operating amount is output to the drive device 19 (step S2).

Thereafter, it is determined whether the operating state calculated based on the state detection values from the sensors 20 to 22 is the optimum operating efficiency state determined in advance (step S3). When it is determined that the optimum operating efficiency state is reached,
At that point, the control is terminated and the vane angle according to the selected operation program is maintained; however, if it is determined that the operating condition is not optimal, the control output (vane angle) according to the selected operation program is corrected. The output is re-outputted (step S4), and it is determined from the state detection value whether the efficiency has improved (step S5).

In this way, the operating status of each stage is fed back, and it is monitored whether the pre-programmed combination of angles of the inlet guide vanes 11 to 14 and diffuser vanes 15 to 18 of each stage is optimal. Control is performed to modify the combination of vane angles in the operating program so that optimum operating efficiency can be obtained at all times in response to changes in operating conditions such as changes in performance and performance (step S6).

By the way, in order to control a multi-stage centrifugal compressor so that a predetermined air capacity can always be obtained with optimum operating efficiency according to various operating conditions, in addition to the above-mentioned control means, there has been a conventional method disclosed in Japanese Patent Application Laid-Open No. 55-123394. There are also control means as disclosed in Japanese Patent Publication No. 56-66490.

In the former control means, when controlling the flow rate toward the target flow rate, the control device controls the predetermined inlet guide vane 1 as in the above-mentioned control means.
After reaching a predetermined region close to the target flow rate by combining the angles of the inlet guide vanes 11 to 14 and the differential user vanes 15 to 18, the angles of the inlet guide vanes 11 to 14 and the differential user vanes 15 to 18 are finely adjusted. We are searching for high efficiency points.

In addition, in the latter control means, the entrance guide vanes 11 to 14 and the differential user vanes 15 to 18
Instead of controlling the angle of the inlet guide vane 1
1 (see FIG. 8) and the rotation speed of the drive device 2 (see FIG. 8), and as shown in FIG. , a rotation speed sensor 24 for detecting the rotation speed of the drive machine 2 , and a drive machine control device 25 for controlling the rotation speed of the drive machine 2 . Then, as a manipulated variable for realizing the optimum operating state for various operating states expressed by air flow rate, temperature, pressure, etc. in the entire centrifugal compressor 1 or the multi-stage compressors 4 to 7,
Operation table for optimal combination values of the angle of the inlet guide vane 11 and the rotation speed of the drive machine 2 (corresponding to the suction flow rate, the angle of the inlet guide vane 11 and the rotation of the drive machine 2 to obtain the optimal operating efficiency) (the given number) is programmed and stored in the storage unit 26 in the control device 23A in advance.

Then, as shown in FIG. 10, the control device 23
Upon receiving the state detection values from the sensors 20 to 22, 24, A calculates and monitors the current operating state (operating conditions, suction flow rate, etc.) of the multistage centrifugal compressor from the detected values (step T1). Corresponding to the operating state, especially when the suction flow rate changes due to a change in operating conditions, the operating amount that can realize the optimum operating efficiency is determined based on the operating table in the storage unit 26, and the operating amount is It is output to the drive device 19A and the drive machine control device 25.

That is, the operating states of the drive machine 2 and the inlet guide vane 11 at the present time are compared with the operating table in the storage section 26 (step T2), and it is determined from the comparison result whether or not the operating efficiency is optimal (step T2). T3).

At this time, if it is determined that the operating efficiency is optimal, the control is terminated at that point and the operating state (vane angle and rotation speed) is maintained; however, if it is determined that the operating efficiency is not optimal, the inlet guide After the angle of the vane 11 and the rotation speed of the drive machine 2 are corrected based on the operation table, the obtained operation amount is output to the drive device 19A and the drive machine control device 25 (step T4).

[Problem that the invention seeks to solve]

However, in any case, in the conventional centrifugal compressor control means as described above, the angles of the inlet guide vanes 11 to 14 and the differential user vane 15 are
It is necessary to set in advance the combination of the angles of ~18 or the angle of the inlet guide vane 11 and the rotation speed of the drive machine 2. There is a problem in that a considerable trial run period is required before actual operation or at the beginning of operation, and in particular, a huge amount of data is required to preset the optimal combination for one year's operating conditions.

In addition, each control means has three control operation variables for the centrifugal compressor 1, namely, the angle of the inlet guide vanes 11 to 14, and the angle of the differential user vanes 15 to 1.
8 angle and drive 2 (that is, centrifugal compressor 1
Since only two of the rotational speeds (rotational speed) are used as control manipulated variables, the control efficiency is lower than when all three are used as control manipulated variables, and it is difficult to reach the target flow rate and optimal efficiency. It takes too long. Therefore, it is conceivable to handle the above three control manipulated variables at the same time, but in the above-mentioned control means, appropriate combinations must be set in advance. When there are three, it becomes extremely difficult and it is impossible to actually realize control.

The present invention aims to solve these problems, and it is possible to achieve the target flow rate while always maintaining high efficiency and with a minimum number of operations, without requiring the above-mentioned test run period or huge amount of data. The purpose of the present invention is to provide a method of controlling a centrifugal compressor that can achieve the following.

[Means for solving problems]

Therefore, in the first centrifugal compressor control method according to the present invention, first, the actual flow rate is controlled at at least four points by manipulating the angles of the inlet guide vane and the diffuser vane and the rotational speed of the centrifugal compressor. , the effective efficiency is measured, and these basic points are used as vertices to form a three-dimensional control amount space with the angle of the inlet guide vane, the angle of the differential user vane, and the rotation speed of the centrifugal compressor as the axes. Develop multiple extrapolation points for the angles of the inlet guide vanes and diffuser vanes and the rotational speed of the centrifugal compressor so as to surround the polyhedron, and calculate the flow rate and efficiency for each of these extrapolation points as described above. Then, from among these extrapolation points, select an extrapolation point that is close to the target flow rate and has high efficiency, and the above-mentioned inlet guide vane and The flow rate of the centrifugal compressor is controlled based on the angle of the diffuser vane and the rotation speed of the centrifugal compressor.

Further, in the second centrifugal compressor control method according to the present invention, in the same manner as the first method, first, the angles of the inlet guide vane and the diffuser vane and the rotation speed of the centrifugal compressor are determined. By operating, the actual flow rate and effective efficiency are measured at least 4 points, and these first basic points are taken as the apex,
The inlet guide vanes and the differential are arranged so as to surround a polyhedron formed in a three-dimensional control amount space whose axes are the angle of the inlet guide vane, the angle of the differential user vane, and the rotational speed of the centrifugal compressor. A plurality of first extrapolation points are developed for the angle of the user vane and the rotation speed of the centrifugal compressor, and for each of these first extrapolation points, the flow rate,
Efficiency is predicted from the above basic points, and then an extrapolation point that is close to the target flow rate and has high efficiency is selected from among these first extrapolation points, and the result is determined by this selected extrapolation point. The flow rate of the centrifugal compressor is controlled based on the angles of the inlet guide vanes and diffuser vanes and the rotation speed of the centrifugal compressor, and After that, measure the actual flow rate and effective efficiency after the operation with the rotation speed, and then measure the three points of the first basic points above and the angles of the inlet guide vane and differential user vane selected last time. The four points of the actual measurement point after the operation of the rotation speed of the centrifugal compressor and the above-mentioned centrifugal compressor rotation speed are set as the second basic points, and the second basic points are set in the same manner as the first time. Expand the multiple extrapolation points,
The first centrifugal compressor is controlled, and the subsequent centrifugal compressors are controlled in the same manner.

[Effect]

In the first and second centrifugal compressor control methods of the present invention described above, three control operation amounts for the centrifugal compressor are controlled, namely, the angle of the inlet guide vane and the diffuser vane, and the centrifugal compression. The centrifugal compressor can be easily controlled by simultaneously using the machine's rotational speed without requiring a trial run period or a huge amount of data.

[Embodiments of the invention]

Hereinafter, a method for controlling a multi-stage centrifugal compressor according to an embodiment of the present invention will be explained with reference to the drawings. FIG. 1 is a flowchart thereof. First, before explaining the method according to this embodiment, FIG. The configuration of a multi-stage centrifugal compressor to which the method of this embodiment is applied and the control device for the multi-stage centrifugal compressor will now be described. Incidentally, in FIG. 2, the same reference numerals as in FIG. 8 indicate substantially the same parts, so a description thereof will be omitted. However, in the multistage centrifugal compressor to which the control device of the present embodiment shown in FIG.
Although the multi-stage centrifugal compressor in the figure is different, the method of the present invention can also be applied to the multi-stage centrifugal compressor in FIG.

As shown in FIG. 2, in the multistage centrifugal compressor in this embodiment, inlet guide vanes (GV) 11 to
14 are inlet guide vane drive devices 19a, respectively.
-19d, and the differential user vanes (DV) 15-18 are driven by differential user vane drive devices 19e-19h, respectively. In addition, as a sensor,
Flow rate sensor 20, temperature sensor 21, pressure sensor 2
2, a rotation speed sensor 24 for detecting the compressor rotation speed and a humidity sensor 27 are provided.

All detection signals from the sensors 20 to 22, 24, and 27 are input to the control device 28. This control device 28 controls the inlet guide vanes 11 to 14 and the differential user vane 1.
A control amount calculation section 29 that calculates control signals to each of the drive devices 19a to 19h and the drive machine 2 in order to control the angles of 5 to 18 and the rotation speed of the centrifugal compressor 1, respectively, a control amount calculation section 30, and a central Control calculation section 3
1, and a control command input section 32 for inputting control command signals to the central control calculation section 31.

Here, the central control calculation unit 31 controls the sensors 20 to
It has a function of receiving detection signals from 22, 24, and 27, calculating the operating state of the multistage centrifugal compressor from these detection signals, and outputting these detection signals and operating state signals to the three-dimensional manipulated variable control calculation section 30. ing. In addition, the control amount calculation section 30 calculates the optimum vane angle control amount and rotation speed control amount that can approach the target flow rate while maintaining the optimum efficiency state, based on the operating state signal from the central control calculation section 31, as shown in FIG. The operation amount calculation section 30 actually controls each vane angle and the compressor rotation speed based on the vane angle control amount and rotation speed control amount from the control amount calculation section 29. The operation amount of each of the drive devices 19a to 19h and the drive machine 2 is calculated and outputted.

Up to this point, we have described the control device for a centrifugal compressor to which the method of the present embodiment is applied. Below, we will explain the part directly related to the method of the present invention, that is, the part when controlling the flow rate in the centrifugal compressor 1. A method for determining the control amount of the vane angle and the rotation speed of the centrifugal compressor 1 (driver 2) (that is, the operation of the control amount calculating section 29) will be explained with reference to FIG. 1 and FIGS. 3 to 7.

In the method of this embodiment, a four-stage centrifugal compressor 4 to 7
However, when controlling the vane angle, controlling the inlet guide vanes 11 to 14 and the differential user vanes 15 to 18 in each stage separately and independently makes the control operation extremely complicated and complicated. Since it becomes complicated and the convergence becomes unstable, the angles of the entrance guide vanes 11 to 14 and the differential user vanes 15 to 18 are made dimensionless and represented by a set of dimensionless entrance guide vane angle α and dimensionless differential user vane β. This simplifies control operations.

First, the definitions and meanings of the dimensionless inlet guide vane angle α and the dimensionless diffuser vane β will be briefly explained with reference to FIGS. 3a and 3b. Generally, as a characteristic of a centrifugal compressor, there is a flow rate-discharge pressure (Q-P) curve as shown in FIG. 3a. If the centrifugal compressor has a single stage, there is naturally only one characteristic curve, so there is no need to make the angles of the inlet guide vane and diffuser vane dimensionless. As shown in Figure 3b, the characteristic curves are different for each stage of centrifugal compressor.

Therefore, when the pressure (discharge pressure P) is almost constant due to the resistance on the device side, each inlet guide vane 11 to 1
4 is one dimensionless inlet guide vane angle such that the operating flow rates Q1 to Q4 of centrifugal compressors 4 to 7 in each stage have similar operating flow rates at the same ratio to the design flow rate Q _D (=Q1). In addition to expressing it as α, each differential user vane 15 to 18 also has a design flow rate Q _D (=Q
1) is expressed as one dimensionless diffuser vane angle β that provides a similar operating flow rate with the same ratio.

That is, in FIG. 3b, if the angles of the diffuser vanes 15 to 18 are constant at the designed value, the pressure ratio distribution at each stage is unchanged, and the design discharge pressure P _D at a certain stage is constant, each inlet guide vane Flow rates Q1 to Q4 are determined for angles 11 to 14. The ratio Q2/Q1, Q3/ to these design flow rates Q _D (=Q1)
The angles GV ₁ to GV ₄ of the inlet guide vanes 11 to 14 of each stage such that Q1, Q4/Q1 are the same are expressed as a dimensionless inlet guide vane angle α as shown in the following equation (1).

α=Knα・(αn/αno−1) …(1) Here, αn is the angle of the n-th stage entrance guide vane, dno is the reference angle of the n-th stage entrance guide vane,
Knα is a coefficient of the n-stage inlet guide vane angle determined so that the n-stage operating flow rate is similar to the design flow rate Q _D for each stage.

Also, in exactly the same way as this dimensionless entrance guide vane angle α, the differential user vanes 15 to 15 of each stage are
The angle of 18 is also expressed as a dimensionless diff user vane angle β as shown in the following equation (2).

β=Knβ・(βn/βno−1) …(2) Here, βn is the angle of the n-stage differential user vane, βno is the reference angle of the n-stage differential user vane, and Knβ is the angle of the n-stage differential user vane. The operating flow rate is determined so that the operating flow rate at each stage is similar to the design flow rate _QD .
This is the coefficient of the diff user vane angle of the stage.

Then, in the control amount calculation unit 29, the angles of the inlet guide vanes 11 to 14 and the differential user vanes 15 to 18 are determined in advance by a set of dimensionless inlet guide vane angle α and dimensionless differential vane defined as described above. Each is expressed as a user vane β, and then, following the flow shown in Figure 1,
The vane angle and rotation speed control amounts are determined in a three-dimensional control amount space with each axis being the dimensionless vane angles α and β and the rotation speed N of the centrifugal compressor 1 (the vane angle and rotation speed explained here). The method for determining the control amount is called the extrapolation method).

When controlling the flow rate in the centrifugal compressor 1 by the control device shown in FIG.
The flow shown in FIG. 1 is started, and first, in the three-dimensional control amount space α-β-N, as shown in FIG.
Four suitable points A, B, C, D including the same point A in the vicinity of
(basic point) is selected (step A1). and,
Regarding the four selected basic points A, B, C, and D,
The operation amount calculation unit 30, the drive devices 19a to 19h, and the drive device 2 actually operate the inlet guide vane 11.
~14. Drive the diffuser vanes 15 to 18 and the driver 2, and measure the flow rate Q and efficiency η at each point A, B, C, and D (step A2).
Here, the flow rate Q is detected by the flow rate sensor 20 and passed through the central control calculation unit 31 to the control amount calculation unit 29.
while the efficiency η is input to the sensors 20 to 22
is calculated in the central control calculation section 31 based on the detection signal from the control amount calculation section 29.

In step A3, the three-dimensional control amount space α
-β-N, a plurality of first extrapolation points (four in this embodiment) are expanded and set so as to surround a triangular pyramid having the first basic points A to D as vertices. Then, the flow rate and efficiency at each extrapolation point ~ are predicted from the actual flow rate and actual efficiency at the basic points A ~ D (step A4).

In other words, the flow rate Q and efficiency η have a characteristic curved surface as shown in Figures 4 and 5 (for flow rate, Q ₁ > Q ₂ ,
Regarding efficiency, η ₁ > η ₂ ), and for flow rate Q and efficiency η at the extrapolation point, the triangular pyramid formed by the extrapolation point and triangle ABD has the same shape as the triangular pyramid ABCD at the actual measurement point. If the extrapolation points are set in this way, the prediction can be easily estimated from the actual measurement points A, B, and D. Note that the flow rate Q and efficiency η at other extrapolation points ~ are also estimated in the same manner as described above.

By the way, in the three-dimensional controlled variable space α-β-N, the flow rate Q and the efficiency η generally have the tendency as shown in FIGS. 4 and 5 (characteristic curved surfaces: Q ₁ and Q ₂ are equal _flow surfaces, η ₂ has an isoefficient surface). In particular, in the figure, there is a relationship Q ₁ > Q ₂ regarding the flow rate, and there is a flow rate increase/decrease relationship in which the flow rate always increases as the vane angles α, β and rotation speed increase, so this relationship can be calculated in advance by calculating the control amount. The flow rate is set and stored in the section 29, and the reliability of the flow rate actually measured in step A2 is verified in steps A5 and A6.

That is, for the first basic points A to D shown in FIG. 6, it is clear from the above relationship that between basic points A and B, the flow rate at point B is always larger than the flow rate at point A. , step A2
Of the actual measured flow rates at each basic point A to D, basic points A and B are compared with the pre-stored flow rate increase/decrease relationship (step A5), and if the increase/decrease relationship is reversed, the comparison is performed. It is determined that the result causes a logical error (step A6), and it is determined that the measurement error by the flow rate sensor 20 is large, so the data acquisition based on this actual measured flow rate is canceled and the actual measured flow rate is determined again. Return to step A2. Furthermore, if it is determined that the above comparison result does not cause a logical pre-emption (step A6), the process moves to the next step A7. In this way,
By verifying the reliability of the actual measured flow rate, it is possible to control the vane angle and rotation speed without losing sight of the target flow rate due to fluctuations in the flow rate measured during control execution or measurement errors. It becomes like this.

If it is determined in step A6 that the above comparison result does not cause a logical pre-emption, then in step A7, the predicted flow rate is determined from the first extrapolation points ~ to the target flow rate.
Select an extrapolation point that is close to Q _P and has a high predicted efficiency.

Next, in step A8, it is determined whether the extrapolation point selected in step A7 falls within the surging region. Although not shown, the surging region can be defined by a surging prevention surface in the three-dimensional control amount space α-β-N. Therefore, in the control amount calculating section 29, the surging prevention surface that defines the surging area is set and stored in advance as a function of the dimensionless vane angles α, β and the rotation speed N, and the extrapolation point is determined in step A7. Each time a selection is made, it is checked whether the extrapolated point crosses the anti-surging surface and enters the surging region.

If the selected extrapolation point is within the surging region, select from among the extrapolation points other than the currently selected extrapolation point that the predicted flow rate is close to the target flow rate Q _P and the predicted efficiency is After selecting the higher value (step A9), it is checked again in step A8 whether or not the extrapolated point falls within the surging region. By repeating this, an extrapolation point that is close to the target flow rate Q _P and has high efficiency is selected from extrapolation points other than the extrapolation points within the surging region.
In this way, it is possible to reliably prevent surging from occurring as a result of controlling the vane angle and rotation speed.

When a highly efficient extrapolation point that is close to the target flow rate and does not fall into the surging region is selected [here, it is assumed that the extrapolation point in Fig. 6 has been selected], the coordinates of this extrapolation point are Vane angles α and β of a set of dimensionless inlet guide vane angle α, dimensionless differential user vane angle β, and rotation speed N
, the actual inlet guide vanes 11~ at each stage
14 and the angles of the diffuser vanes 15 to 18 (step A10).

In other words, from equations (1) and (2) mentioned above, the vane angles αn and βn (in this example, n=1 to
4).

In step A10, which calculates the actual vane angles αn and βn from the dimensionless vane angles α and β, if a disturbance causing variation in the operating point is detected in any of the centrifugal compressors 4 to 7, the following steps are performed: The deviation of the operating flow rate from the similar operating flow rate in the centrifugal compressor of the stage in which the disturbance occurred can be corrected.

Operating characteristics of each stage (bed H, suction flow rate of the next stage)
Q ₂₀ ) is generally expressed as the following equation.

H=x・R・T ₁・{(P ₂ /P ₁ ) ^k-1/k −1}/(x-1)
...(3) Q ₂₀ ∝1/P ₂ ...(4) Here, x is the specific heat ratio, R is the gas constant, T ₁ is the suction temperature, P ₁ is the suction pressure, and P ₂ is the discharge pressure.

The angles of the inlet guide vanes 11 to 14 and the diffuser vanes 15 to 18 of each stage are set from the dimensionless vane angles α and β to (1), ( Even if it is determined by equation 2) and given as the manipulated variable, if only the suction temperature of a certain stage becomes relatively low due to a disturbance, the head (suction pressure) H of the centrifugal compressor that caused the disturbance will change. Therefore, from equation (3), the discharge pressure
_P2 becomes larger. As a result, according to equation (4), the suction flow rate Q ₂₀ of the next stage decreases, and the similar operation flow rate changes.

Due to this disturbance, the operating flow rate at each stage is similar to the design flow rate, which may result in a decrease in efficiency due to poor matching of operating points, or surging may occur early in a certain stage. As a result, the operating range becomes narrower.

Therefore, as shown in equations (5) and (6), in order to cancel the disturbance based on the detected disturbance, the dimensionless correction amount [Knα・A ₁・(αnt /αno), etc.],
From equations (5) and (6) obtained by adding each dimensionless correction amount to the dimensionless inlet guide vane angle α and the dimensionless differential user vane angle β, The angles αn and βn of the fuser vanes are found.

α=Knα・{αn/αno+A ₁・(αnt/αno) +A ₂・(α _oRH /αno)+…−1}…(5) β=Knβ・{βn/βno+B ₁・(βnt/ βno) +B ₂・(β _oRH /βno) +...-1}...(6) Here, αnt is the amount of disturbance correction due to the suction temperature of the nth stage, α _oRH is the amount of disturbance correction due to the humidity of the nth stage, βnt
is the disturbance correction amount due to the suction temperature of the nth stage, β _oRH is n
Disturbance correction amount due to humidity in the tier, A ₁ , A ₂ , B ₁ , B ₂
is the coefficient.

In this way, even when searching for a highly efficient extrapolation point that is close to the target flow rate Q _P , it is possible to correct the deviation of the operating flow rate from the similar operating flow rate in the centrifugal compressor where disturbance has occurred. Furthermore, by this modification, the flow rate at each stage can always be made to be a similar operating flow rate to the design flow rate.

As described above, if there is a stage where a disturbance occurs, equations (5) and (6) are used, and when there is no stage where a disturbance occurs, equations (5) and (6) are replaced by (1), Equation (2) is obtained, and from a set of dimensionless entrance guide vane angle α and dimensionless differential user vane angle β, the actual entrance guide vanes 11 to 14 and differential user vanes 15 to
18 angles are found.

Then, control signals are outputted from the operation amount calculating section 30 to the drive devices 19a to 19h and the drive machine 2 according to the obtained angle and rotation speed N, and the control signals are outputted to the inlet guide vanes 11 to 14 and the differential user vane 15.
-18 are driven and controlled (step A11).

After that, it is determined whether the difference between the flow rate Q changed by the above flow rate control and the target flow rate Q _P is smaller than the flow rate tolerance value ΔQ (step A12), and the flow rate difference is determined as the flow rate tolerance value ΔQ. If the flow rate difference is smaller than Q, the flow rate control ends at that point, while if the flow rate difference is greater than or equal to the flow rate tolerance ΔQ, the process returns to step A3.
Return to , select four new basic points, and perform steps A1 to A12 in the same way as above for the second extrapolation points expanded to surround these basic points.
Execute.

Here, the basic point selected for the second time is the first
Three points A, B, and D of the actual measurement points of the first measurement, and the entrance guide vanes 11 to 14 and the differential user vanes 15 to 1 selected in the first measurement are determined at step A12.
8 and the actual measurement point that was the extrapolation point where the flow rate and efficiency were actually measured after operating the drive machine 2.A new second extrapolation point was set around these basic points, and each Predict the flow rate and efficiency at the location of the extrapolation point.

In this way, until the conditions in step A12 are met, the inlet guide vanes 11-14
and operate differential user vanes 15 to 18,
The flow rate and efficiency are actually measured, and then extrapolation points are developed around the basic point to find an extrapolation point that is close to the target flow rate Q _P and has high efficiency, and the vane angle and rotation speed of the centrifugal compressor 1 are controlled. It is.

In this embodiment, the extrapolation points around the basic point are developed as shown in Fig. 6, but the range in which the extrapolation points can be set is arbitrary, and the target flow rate Q _P is set to the current flow rate. When the target flow rate Q P is far from Q, the height of the triangular pyramid based on the basic point may be expanded, or when the target flow rate Q _P is close to the current flow rate Q, it may be decreased. Also, instead of the extrapolation point ~ shown in Figure 6, as shown in Figure 7, the point ~ at the position where the triangular pyramid formed by the basic points A to D is similarly expanded or similarly reduced is set as the extrapolation point. Good too.

Furthermore, in this embodiment, the number of basic points is four, but the number is not limited to four.
There may be more than one.

As described above, according to the method of this embodiment, the operating point that optimizes the efficiency is directly searched, and the inlet guide vanes 11 to 14 and the differential user vanes 15 to
Since the flow rate control in the centrifugal compressor 1 is performed while controlling the angle of the vane 18 and the rotation speed of the centrifugal compressor 1 at the same time, there is no need to program the combination of vane angles in advance as in conventional means. The advantage is that the flow rate can be controlled with a minimum number of operations so as to approach the target flow rate while always maintaining high efficiency.

Furthermore, according to the method of this embodiment, a point close to the target flow rate and with high efficiency can be selected from points other than the extrapolated points within the surging region, so surging does not occur with vane angle control. In addition to reliably preventing this, if there is a logical safeguard in the actually measured flow rate, it is determined that the measurement error is large, which increases the reliability of the detected flow rate value and the control method. be.

Furthermore, in this embodiment, for the multi-stage centrifugal compressor, by using a set of dimensionless inlet guide vane angle α and dimensionless differential user vane angle β, the inlet guide vanes 11 to 14 and Defuser vane 15-1
Since the 8 angles can be handled as one set, it is possible to control a multi-stage centrifugal compressor extremely easily without complicating the control, and it is possible to maintain a good matching condition for each stage. can be obtained. It also has the advantage of realizing a wide operating range and highly efficient operation.

Although the above embodiment describes the case where the method of the present invention is applied to a multi-stage centrifugal compressor, the method of the present invention can also be applied to a single-stage centrifugal compressor. The same effect as the above embodiment can be obtained without using a dimensionless vane angle.

〔Effect of the invention〕

As described above, according to the centrifugal compressor control method of the present invention, in both the first and second methods, the operating point that optimizes the efficiency is directly searched, and the angle of the inlet guide vane and the This makes it extremely easy to control the flow rate in a centrifugal compressor while simultaneously handling three control variables: the angle of the fan vanes and the rotational speed of the centrifugal compressor. This eliminates the need for programming, eliminates the need for test run periods and huge amounts of data, and has the advantage of being able to control the flow rate with a minimum number of operations to approach the target flow rate while always maintaining high efficiency.

[Brief explanation of drawings]

1 to 7 show a method for controlling a centrifugal compressor as an embodiment of the present invention. A block diagram showing the configuration of the device, Figures 3a and 3b are graphs showing flow rate-discharge pressure characteristics to explain the dimensionless inlet guide vane angle and dimensionless diffuser vane angle, and Figures 4 and 5. are graphs showing a flow rate characteristic curve and an efficiency characteristic curve, respectively, in a three-dimensional controlled variable space, FIGS. 6 and 7 are graphs showing a three-dimensional controlled variable space for explaining the extrapolation method in this method, and FIG. 1 is a block diagram showing a general multi-stage centrifugal compressor, and FIGS. 9 and 10 are both flowcharts for explaining the control means of the conventional multi-stage centrifugal compressor. In the figure, 1...centrifugal compressor, 2...driver, 4
~7... Compressor, 8-10... Intercooler, 11-1
4... Inlet guide vane, 15-18... Diffuser vane, 19a-19h... Drive device, 20... Flow rate sensor, 21... Temperature sensor, 22... Pressure sensor, 24... Rotation speed sensor, 27... Humidity sensor, 2
8... Control device, 29... Controlled amount calculation section, 30... Manipulated amount calculation section, 31... Central control calculation section, 32... Control command input section.

Claims (1)

[Scope of Claims] 1 Regarding a centrifugal compressor having a variable-angle inlet guide vane and a differential user vane on the inlet side and outlet side, respectively, the angles of the inlet guide vane and the differential user vane and the centrifugal compressor When controlling the centrifugal compressor by adjusting the rotational speed of the centrifugal compressor, first, the angles of the inlet guide vanes and diffuser vanes and the rotational speed of the centrifugal compressor are controlled to control at least four points. The flow rate and the effective efficiency are measured, and these basic points are used as vertices in a three-dimensional controlled variable space whose axes are the angle of the inlet guide vane, the angle of the differential user vane, and the rotational speed of the centrifugal compressor. A plurality of extrapolation points are developed for the angles of the inlet guide vanes and diffuser vanes and the rotational speed of the centrifugal compressor so as to surround the formed polyhedron, and for each of these extrapolation points, the flow rate,
Efficiency is predicted from the above basic points, and then an extrapolation point that is close to the target flow rate and has high efficiency is selected from among these extrapolation points, and the above inlet is determined by this selected extrapolation point. A method for controlling a centrifugal compressor, comprising controlling the flow rate of the centrifugal compressor based on the angles of guide vanes and diffuser vanes and the rotational speed of the centrifugal compressor. 2. Adjust the angles of the inlet guide vanes and diff user vanes and the rotational speed of the centrifugal compressor for a centrifugal compressor that has variable angle inlet guide vanes and diff user vanes on the inlet and outlet sides, respectively. When controlling the centrifugal compressor, first measure the actual flow rate and effective efficiency at at least four points by manipulating the angles of the inlet guide vane and diffuser vane and the rotation speed of the centrifugal compressor. Then, with these first basic points as the vertices, the angle of the inlet guide vane, the angle of the diffuser vane, and the rotation speed of the centrifugal compressor are formed in a three-dimensional control amount space with each axis as the axes. A plurality of first extrapolation points are developed for the angles of the inlet guide vanes and diffuser vanes and the rotational speed of the centrifugal compressor so as to surround the polyhedron, and each of these first extrapolations is Predict the flow rate and efficiency for each point from the basic points above, then select an extrapolation point that is close to the target flow rate and has high efficiency from among these first extrapolation points, and apply the method to this selected extrapolation point. The flow rate of the centrifugal compressor is controlled based on the angles of the inlet guide vanes and the diffuser vanes and the rotational speed of the centrifugal compressor, and the angles of the inlet guide vanes and the diffuser vanes are Measure the actual flow rate and effective efficiency after operation with the rotational speed of the centrifugal compressor, and then measure the three points of the first basic points and the inlet guide vane and differential selected last time. The four points of the actual measurement points after the operation of the angle of the user vane and the rotation speed of the centrifugal compressor are set as the second basic points, and these second basic points are set as the vertices in the three-dimensional control amount space. A plurality of second extrapolation points are developed for the angles of the inlet guide vane and diffuser vane and the rotational speed of the centrifugal compressor so as to surround the polyhedron formed in After predicting the flow rate and efficiency for each extrapolation point based on the flow rate and efficiency at the second basic point, select from among these second extrapolation points those points that are close to the target flow rate and have high efficiency. selecting an extrapolation point, and controlling the centrifugal compressor based on the angles of the inlet guide vane and the diffuser vane and the rotational speed of the centrifugal compressor determined by the selected extrapolation point; A method for controlling a centrifugal compressor, characterized in that the centrifugal compressor is controlled in the same manner thereafter.